Question about the message to king Belshazzar

25 And this is the writing that was written, MENE, MENE, TEKEL, UPHARSIN.
26 This is the interpretation of the thing: MENE; God hath numbered thy kingdom, and finished it.
27 TEKEL; Thou art weighed in the balances, and art found wanting.
28 PERES; Thy kingdom is divided, and given to the Medes and Persians.

I'm wondering why the last word in the message (UPHARSIN) is different from the last word in the explanation (PERES)
Any help would be cool.

Dan 5:28Peres - In Dan_5:25 this is “Upharsin.” These are but different forms of the same word - the word in Dan_5:25 being in the plural, and here in the singular. The verb (פרסperas) means, to “divide;” and in this form, as in the previous cases, it is, according to Gesenius, participle meaning “divided.” As it stands here, it would be applicable to anything that was “divided” or “sundered” - whether a kingdom, a palace, a house, territory, etc. “What” was divided could be known only by Divine revelation. If the “word” had been understood by Belshazzar, undoubtedly it would have suggested the idea that there was to be some sort of division or sundering, but what that was to be would not be indicated by the mere use of the word. Perhaps to an affrighted imagination there might have been conveyed the idea that there would be a revolt in some of the provinces of the empire, and that a part would be rent away, but it would not have occurred that it would be so rent that the whole would pass under the dominion of a foreign power. Josephus (“Ant.” b. x. ch. xi. Section 3) says, that the word “Phares in the Greek tongue means a “fragment,” κλασμαklasma - God will, therefore, break thy kingdom in pieces, and divide it among the Medes and Persians.”Thy kingdom is divided - That is, the proper interpretation of this communication is, that the kingdom is about to be rent asunder, or broken into fragments. It is to be separated or torn from the dynasty that has ruled over it, and to be given to another.And given to the Medes and Persians - On this united kingdom, see the notes at Isa_13:17. It was “given” to the Medes and Persians when it was taken by Cyrus, and when the kingdom of Babylon became extinct, and thenceforward became a part of the Medo-Persian empire. See the notes at Isa_13:17, Isa_13:19.